High-frequency signaling system



Alllllllll I'VIIIVVV lrm/Qntorl I M His Attor ney \X/albev R. G. Baker,by

'I'I'I W. R. G. BAKER.

mzo SEPT. 11. 1921.

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HIGH FREQUENCY SIGNALING SYSTEM.

Mar. 27, 1-923.

W Q L0 000m 0a a, L 2

Patented Mar. 27, 1923.

UNITED STATES 1,449,722 PATENT OFFICE.

WALTER R. G. BAKER, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERALELECTRIC COMPANY, A CORPORATION OF NEW YORK.

HIGH-FREQUENCY SIGNALING SYSTEM.

Application filed September 17, 1921.

T 0 all whom it may concern:

Be it known that I, IVALTER R. G. BAKER, acitizen of the United States,residing at Schenectady, in the county of Schenectady, State of NewYork, have invented certain new and useful Improvements inHigh-Frequency Signaling Systems, of which the following is aspecification.

My present invention relates to high frequency signaling systems andmore particularly to apparatus of the vacuum tube type for producing andmodulating high frequency oscillations for use in a signaling system.

One of the objects of my invention is to provide a system which will becapable of generating high frequency oscillations and supply them to atransmitting circuit. These may be in the form of speech modulated highfrequency waves such as are used for radio telephony, interruptedcontinuous waves for radio telegraphy or continuous waves for radiotelegraphy. Still another object of my invention is to provide a systerm in which vacuum tubes are employed for modulating the highfrequency waves produced by other vacuum tubes and in which, when thetransmitting equipment is employed for radio telegraphy, modulator tubesmay be utilized for producing high frequency oscillations.

The novel features which I believe to be characteristic of my inventionare set forth with particularity in the appended claims, my inventionitself, however, both as to its organization and method of operation,together with further objects and advantages thereof will best beunderstood by reference to the following description taken in connectionwith the accompanying drawing in which I have shown diagrammatically acircuit arrangement whereby my invention may be carried into effect.

As indicated in the drawing the transmitting equipment comprises aseries of vacuum tubes 1, 2, 3, 1, 5 of the three-electrode or pliotrontype. In the description of the various tubes, 1 and 2 are designated asoscillators, tubes 3 and 4 as modulators, and tube 5 as an amplifier.The filaments in all of these tubes are connected to common bus bars 6and 7 which are supplied with current for lighting the filaments fromthe secondary 8 of an alternating current transformer 9, the middlepoint 10 of the sec Serial No. 501,334.

ondary 8 being grounded. The grid electrodes of the oscillator tubes 1and 2 are connected in parallel and the plate electrodes of these tubesare likewise connected in parallel. The input circuit of the oscillatortubes 1 and 2 comprises a series condenser 11 shunted by the leakresistance 12 and a second series condenser 13 which is shunted by arotatable make and break device 14: in series with a key 15. The inputcircuit is completed to the filament by means of the ground connectionat 16 and ground connection 17 to the middle point of the transformersecondary 8. The output circuits of the oscillators 1 and 2 are suppliedwith energy from a direct current source 18 through an audio frequencyreactance 19 and an inductance 20, the

negative terminal of the direct current source 18 being grounded at 21.The transmitting circuit to which high frequency oscillations are to besupplied in the case illustrated includes an antenna 22 which may beconnected by means of the switch 23 either to the transmitting equipmentby making contact at 24, or to suitable receiving equipment by contact25. In order to provide for the generation of and supply to the antennaof different wave lengths the connection between antenna and earth maybe made through the variable connector 26 to a series of condensers 27,loading inductances 28, the variable loading inductance 29 andinductance 30, which is coupled to the plate inductance 20. Thenecessary coupling between the output circuits of the tubes 1 and 2 andtheir input circuits to permit these tubes to act as generators of highfrequency oscillations is obtained by means of the capacity 31. Theamount of coupling capacity which is most suitable for the differentwave lengths to be generated may be obtained by means of the variableconnector 32.

In case the system is to be employed for radio telephony the outputcircuits of the modulators 3 and 4 are supplied with energy from thesource 18 through the iron core impedance 19 and the radio frequencychoke 33. The sound waves which are to be transmitted for reproductionat the receiving station are impressed upon the telephone transmitter 34which is in a local circuit with the battery 35 and primary 36 of atelephone transformer. The

secondary 37 of the telephone transformer is included in the inputcircuit of the a1npliher 5. The output circuit of the amplifier 5 issupplied with current from a direct cur-- rent source 38 through animpedance 39. The potential variations produced. in the output circuitof the amplifier 5 across the impedance 39 by the potential variationsof circuit of the modulator tubes 3 and 4 and.

the amplitude of the high frequency oscillations generated varies indirect accordance With the variations in the current supplied by themicrophone 34. When the transmit ting equipment isused for radiotelephony the condenser 13 is short circuited by a closure of thekey 15and by contact made through the rotatable make and break device 14 or inany other desired manner.

Nhen it is desired to employ the 'apparatus for radio telegraphy thegrids and anodes of the modulators 3 and 4 may be connected by means ofswitches 41 and 42,. respectively in parallel with the'grids and anodesof oscillators l and 2. The numberof oscillating tubes being thusdoubled the output of the equipment will also be substantially doubled.If desired, the amplifier- 5 may also by suitable connection be employedin parallel with the other tubes as: an oscillator. In order that theapparatus:

may be operated most eiiiciently for the pr'o-- duction of highfrequency oscillations" it is desirable that the average potential ofthe grids should be negative. The grid condenser 11 with the grid leakresistance 12 furnishes the necessary adjustmenttor this such a highnegative charge that the pro purpose and when the modulator tubes areswitched over in parallel with the oscillator tubes the value oi? thisresistance maybe ad justed by means oi the variable connection 43 togive the desired negative potential for the operation oi the four tubesin parallel.

When it is desired to transmit interrupted continuous waves the device'14 is rotated. WVhen the shunt circuit around condenser 13 is broken bymeans of this device the grids of the tubes immediately assume ductionof high frequency oscillations is stopped. When this shunt circuit ismade the negative charge on the grids is permitted to leak off throughthe leak resistance 12 and the connection around condenser 13 and theproduction of oscillations immediately starts.

If the device 14 is rotated at such a speed as to produce interruptionsat an audible fre quency, then when the key 15 is closed high frequencyoscillations will be supplied to the antenna in groups succeeding eachother at an audible frequency. W hen it is desired to transmitcontinuous waves the make and break device 14 is short circuited orstopped at such a point that ,contact is made therethrough and thegeneration othigh frequency waves is interrupted only when the key 15 isopened. A choke coil 44 should be inserted in series with the make andbreak device 14 and the key 15 to prevent high frequency current fromflowing in this shunt circuit. In case the radio choke coil 44 in serieswith the interrupter is insuflicient to prevent radio currents fromtaking this path, a trap circuit may be formed by shunting this chokewith a condenser 61. This trap circuit is tuned to the transmitting wavelength. i

In the operation of the vacuum tubes 3, 4 and 5, it will usually bedesirable to maintain the grids normally at a negative potential Withrespect to the filaments, and for this purpose a biasing battery. 45 maybe employed. This same battery may also, if desired, be employed forfurnishing a biasing potential for the grids of the oscillators by meansof the connection 59. thatthe equipment may be operated to supplydii'l'erent amountsof power, theresistance 46 may be inserted in serieswith the field 4'7 of the generator 18 by means of a switch 48. Theamount of this resistance in the field of the generator may be varied asdesired; andthe amount of power supplied from the generator to theoscillating system thereby varied at will. Whenever the voltage suppliedto the output circuits ofthe tubes is varied it is also usuallydesirable that the potential of the grids of the tubes should be varied.This may be accomplished by means of the s vitch 49, whiclrmay beoperated simultaneously with the switch 48.

1t is'frequently desirable that the trans initting set; should be soarranged that it cannot be operated by inexperienced persons, or withoutpermission oi their superior o'fiicei's. One convenient way ofpreventing such operation at the 1 full power output of the equipmentindicated in the drawing in connection with the means for supplyingpower to the set. A. switch 50 is inserted in the lead 51 by means oiwhich all of the resistance 46 is cut out and this switch is held openby means of a lock 52. Until the lock a2 is removed it will. thereforebe impossible to operate the equipment at its full output.

When the equipment is to be employed for telephone operation it isdesirable in order to lengthen thelife of the tubes as Well as for otherreasons, that the generation of- In order ing the reception: period.This may be accomplished by interrupting the supply of current to theplate circuits. If, however,

the current supplied to the filaments is com- .to the filaments andplate circuits and the time ,when oscillations start. To prevent thisdelay, or at least reduce it to a mlmmum, means may be provided wherebythe current supplied to the filaments of the vacuum tubes will bereduced to such a value .during the reception period that the life ofthe tubes will be greatly increased over their life in case the filamentcurrent should be kept. at its normal value during reception. If thefilament current is restored to its normal value as soon as it isdesired to transmit, oscillations will start sooner than they would ifthe filament current and the consequent heating of the filament had toThe conductors 55 and 56 form a short circuit around the resistance 53so that this resistance is automatically short circuited when thetransmitting equipment is connected to the antenna. When the switch 23is thrown over to the receiving position contact 54 is broken andresistance 53 is efiec tive in reducing the amount of current suppliedto the filaments. V

When the tubes 3 and 4 are being operated as modulators and the tube 5as amplias modulators and amplifiers.

The apparatus should preferably be so arranged and switching meansprovided whereby all of the adjustments of the system for changing thewave length transmitted may be made simultaneously by the operation ofone switch handle. These adjustments in the system illustrated comprisethe variable connections 26 and 82 and also preferably the variableconnection 60 to the plate inductance 20.

As an alternative method of operation to transmit interrupted continuouswaves with the apparatus illustrated and described, the

An auX- This difiiculty may telephone transmitter 34 may be replaced byan interrupter such as the interrupter 14 or a buzzer. If, for example,a buzzer is employed in place of the microphone 34 then when the tubes 1and 2 are employed as '05- cillators, tubes 3 and 4 will act asmodulators and tube 5 as an amplifier. The keying of the system may thenbe accomplished either by means of the key 15 in shunt to condenser 13,or by insertlng a key in the primary circuit of the microphonetransformer. The first method of operation mentioned is preferable, buthas one disadvantage in that plate current will be taken by tubes 3, 4and 5 whether the key 15 is up or down. In order to prevent this thepositive terminal of the biasing battery 45 instead of being connecteddirectly to ground, as shown, may be connected through the connection 59to ground through the condenser 13, the negative terminal of the battery45 being connected to the grids of tubes 3, 4 and 5 by means of theswitch 49. These grids will then when the key 15 is open, receive anegative potential suiticient to cut off the plate current.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is

1. The combination in a high frequency transmitting apparatus of aplurality of vacuum tubes. adapted to act as oscillation generators andmodulators when the apparatus is used for high frequency telephonetransmission and means whereby the modu lator tubes may also be employedto serve as oscillation generators when the apparatus is employed fortelegraph transmission.

2. The'combination in a high frequency transmitting apparatus of .aplurality of vacuum tubes having input and output circuits, the inputcircuit of at least one of said tubes being coupled by capacity to theoutput circuit wherebythe tube will act as a high frequency oscillationgenerator, means whereby one of said tubes will act as a modulator ofthe high frequency oscillations generated and means whereby themodulator transmitting system of a transmitting circuit, a plurality ofvacuum tubes adapted to act as oscillation generators and modulators forgenerating'and modulating high frequency oscillations and supplying themto the transmitting circuit and means wherei by the modulator tubes maybe connected in parallel with the oscillator tubes to assist in thegeneration of high frequency oscillations.

4. The combination in a high frequency transmitting'system of atransmittinglcirfi suit, a plurality of vacuum tubes having in at leastone of saidtubesbeing coupled to the transmitting circuit and the inputcircuit of said tube being coupled by capacity to the transmittingcircuit whereby the tube will act as a generator of high frequencyoscillationswhich will be supplied to the transmitting circuit, meanswhereby another of said tubes will act as a modulator of the highfrequency oscillations supplied to the transmitting circuit, and meanswhereby the modulator tube circuits may also be connected in parallelwith the oscillator tube circuits and thereby assist in the generationfrequency oscillations.

he combination in a high frequency transmitting system of a transmittincircuit, means for varying the tuning of said transmitting circuit, aplurality of vacuum tubes having input and output circuits,-the outputcircuit of at least one of said tubes being coupled to the transmittingcircuit and the input circuit of said tube being coupled by capacity tothe transmitting circuit whereby the tube will act as a generator ofhigh frequency oscillations which will be supplied to the: transmittingcircuit, means for varying the amount of capacity coupling, meanswhereby another of said tubes willact as a modulator of the highfrequency oscillations supplied to the transmitting circuit and meanswhereby the modulator tube circuits may also be connected in parallelwith the oscillator tube circuits and thereby assist in the generationof high frequencly oscillations.

6. he combination in a high frequency transmitting system of atransmitting circuit, a plurality of vacuum tubes adapted to act asoscillation generators and modulators for generating and modulating highfrequency oscillations and supplying them to the transmitting circuit,means whereby the modulator tubes may be connected in parallel with theoscillator tubes to assist in the generation of high frequencyoscillations, and means for-interrupting in a regular and predeterminedmanner the generation of oscillationsvwhen all of the tubes are employedas oscillators.

7. The combination in a high frequency transmitting system of atransmitting circuit, a plurality of vacuum tubes having input andoutput circuits, the output circuit of at least one of said tubes beingcoupled to the transmitting circuit and the input circuit of said tubebeing coupled by capacity to the transmitting circuit whereby the tubewill act as a generator of high frequency oscillations which Will besupplied to the transmitting circuit, means whereby another of saidtubes will act as a modulator of the high frequency oscillationssupplied to the transmittmg circuit, means whereby the modulator tubecircuits may also be conthe input circuit of said tube being coupledv bycapacity to the transmitting circuit whereby the tube will act as agenerator of high frequency oscillations which will be supplied to thetransmitting circuit, means for varying the amount of capacity coupling,means whereby another of said tubes will act as a modulator of the highfrequency oscillations supplied to the transmitting circuit, meanswhereby the modulator tube circuits may also be connected in parallelwith,

the oscillator tube circuits and thereby assist in the generation ofhigh frequency oscillations, and means for interrupting in a regular andpredetermined'manner the generation of oscillations when all of thetubes are employed as oscillators.

9. The combination in a high frequency transmitting apparatus of aplurality of vacuum tubes having input and output circuits, the inputcircuit of at least one of said tubes being coupled by capacity to theoutput circuit whereby the tube will act as a high frequency oscillationgenerator, means whereby one of said tubes will act as a modulator ofthe high frequency oscillations'generated, means whereby the modulatortube circuits may also be connected in parallel with the oscillator tubecircuits and thereby assist in the generation of high frequencyoscillations and means for maintaining normally a negative potentialupon the input electrode of the oscillator tube, said means beingadapted to be adjusted tomaintain substantially the same negativepotential upon the input electrodes of all of the tubes when themodulator tube is employed to generate oscillations.

10. The combination in a high frequency transmitting system of atransmitting circuit, a plurality of vacuum tubes having in put andoutput circuits, the output circuit of at least one of said. tubes beingcoupled to the transmitting circuit and the input circuit of said tubebeing coupled by capacity to the transmitting circuit whereby the tubewill act as a generator of high frequency oscillations which will besupplied to, the transmitting circuit, means whereby another of saidtubes act as a modulator of the hi h freque cy oscillations supplied tothe transmitting circuit, means whereby v the modulator tube circuitsmay also be connect ed in parallel with the oscillator tube cir-- cuitsand thereby assist in the generation of high frequency oscillations, andmeans for maintaining normally a negative potential upon the inputelectrode of the oscillator tube said means being adapted to be adjustedto maintain substantially the same negacuits the input circuit of atleast one tube being coupled to the output circuit so that the tube willact as a high frequency oscillation generator, means whereby at leastone of said tubes will act as a modulator of the high frequencyoscillations generated,means whereby the input circuit of the modulatortube may be connected in parallel with the input circuit of theoscillator tube, and means common to the input circuits of all of thetubes for interrupting in a regular and predetermined manner thegeneration of oscillations.

12. The combination in a high frequency transmitting apparatus of aplurality of vacuum tubes having input and output circuits, the inputcircuit of at least one tube being coupled to the output circuit so thatthe tube will act as a high frequency oscillation generator, meanswhereby at least one of said tubes will act as a modulator of the highfrequency oscillations generated, means whereby the input circuit of themodulator tube may be connected in parallel with the input circuit ofthe oscillator tube and a rotatable make and break device connected incommon to the input circuits of all of the tubes for interrupting in aregular and predetermined manner the generation of oscillations.

13. The combination in a high frequency transmitting apparatus of aplurality of vacuum tubes having input and output circuits, the inputcircuit of at least one tube being coupled to the output circuit so thatthe tube will act as a high frequency oscillation generator, meanswhereby at least one of said tubes will act as a modulator of the highfrequency oscillations generated, means whereby the input circuit of themodulator tube may be connected in parallel with the input circuit ofthe oscillator tube, a rotatable make and break device connected incommon to the input circuits of all of the tubes, said make and breakdevice being arranged in such a way that when the connection is brokenthereby a sufliciently high negative potential will automatically beimpressed upon the input electrodes to interrupt the generation ofoscillations.

14:. The combination in a high frequency transmitting apparatus of aplurality of vacuumtubes having input and output circuits the inputcircuit of at least one tube being coupled to the output circuit so thatthe tube w1ll act as a high frequency oscilla-.,

tion generator, means whereby at least one ofsaid tubes will act as amodulator. of the high frequencyoscillations generated means whereby theinput circuit of the modulator tube may be connected in parallel withthe input circuit of the oscillator tube, a common portion of all of theinput circuits thus:

connected including a series condenser shunt ed by a resistance whichmay be varied in accordance with variations in the number of L tubeswhose input circuits are connected in: parallel and a second seriescondenser which is shunted by a rotatable make and break device with akey in series therewith.

15. The combination in a high frequency transmitting system of atransmitting circuit, a plurality of vacuum tubes having input andoutput circuits, the output circuit of at least one of said tubes beingcoupled to the transmitting circuit and the input circuit of said tubebeing coupled by capacity to the transmitting circuit whereby the tubewill act as a generator of high frequency oscillations which will besupplied to the transmitting circuit, means whereby another of saidtubes will act as a modulator of the high frequency oscillationssupplied to the transmitting circuit, means whereby the modulator tubecircuits may also be connected in parallel with the oscillator tubecircuits and thereby assist in the generation of high frequencyoscillations, a common portion of all of the input circuits thusconnected including a series condenser shunted by a resistance which maybevaried in accordance with variations in the number of tubes whoseinput circuits are connected in parallel, and a second series condenserwhich is shunted by a rotatable make and break device with a key inseries therewith.

16. The combination in a radio signaling system of an antenna, a vacuumtube transmitting set adapted to supply high frequency oscillations tosaid antenna, switching means for connecting said antenna to saidtransmitting set or to a receiving set, and means adapted. to beoperated simultaneously with said switching means for reducing theamount of current supplied to the filaments of the vacuum tubes of thetransmitting set when the antenna is connected to the receiv ing set.

17. The combination in a radio signaling system of an antenna, a vacuumtube trans mitting set adapted to supply high frequency oscillations .tosaid antenna, a source of current for supplying heating current to thefilaments of the vacuum tubes of said transmitting set, a resistance inseries with said source, switching means for connecting said antenna tosaid transmitting set or to a receiving set, and means adapted to beoperated simultaneously with said switching means for short circuitingsaid resistance when the antenna is connected to the transmitting setand removing the short circuit from said resistance when the antenna isconnected to the receiving set.

18., The combination in a high frequency signaling system of a vacuumtube generating'equipment for supplying high frequency oscillations, asource of energy for said equipment, means for varying the amount ofenergy supplied by said source to said equipment, and means associatedwith the means for varying the energy supply for preventing theunauthorized use of the generating q pme 19. The combination in a highfrequency signaling system, of a vacuum tube generating equipment forsupplying high frequency oscillations, a source of energy for saidequipment, means for varying the amount of energy supplied by saidsource to said equipment, and means associated with the means forvarying the energy supply for preventing the unauthorized use of thegenerating 7 equipment with its maximum output.

In witness whereof, I have hereunto set my hand this 16th day ofSeptember, 1921.

WALTER R. G. BAKER.

